Penetrating capability of the perforating jet i.e. the maximum possible depth of penetration thereof and, in particular, the maximum possible depth of cutting, depends on the shape of the charge hollow, thickness of the layer of explosive material over the charge hollow, density of the explosive material and some other factors.
Until quite recently mainly two first above factors were taken into consideration when the design of an extended shaped charge was to be improved. A problem to increase the density of the explosive to be fitted into the cavity of the charge was solved separately without taking account of the charge design.
In the existing extended shaped charges with a conical or curvilinear charge hollow the liner thereof is attached to the outer shell of the charge normally by means of welding, glue or lock joint, and form therewith a cavity filled with an explosive (see, or example, U.S. Pat. Nos. 3,176,613, 3,251,300, 3,777,663). A body assembled from separate pieces makes it easier to form a charge of any desired shape but does not permit the density of an explosive contained in the cavity of the body to be increased.
Known in the art, for example, is an extended shaped charge wherein a convex outer shell and a liner of the charge hollow, concaved towards the outer shell, form a cavity filled with a high explosive. The outer shell of the charge is made of plastic material and has a shape of the cylinder. The liner of the charge hollow is a copper partition fitted inside the cylinder formed by the outer shell, and separating the cavity containing explosive from the charge hollow which is filled with gas in order to ensure a shaped charge effect when the charge is used under water. The liner of the charge hollow has a shape of a cylinder section so that the cavity to receive explosive is defined, in the cross section of the charge, by intersecting circular arcs of the two cylinders (see FRG Pat. No. 2428435, 1975).
The design of the above charge provides for separate manufacture of the outer shell and the liner of the charge hollow, which are subsequently assembled to form a body of the charge. An explosive material fitted into the cavity of the body is formed by casting and has, therefore, voids decreasing the density thereof.
It should be noted that the body of the charge of the above design allows a power explosive material to be used in the charge but the density of such explosive material filled in a loose state is lower (about 1 kg/cm.sup.3) than that of the cast explosive. Compacting the powder explosive material during the process of its being filled is a dangerous and expensive additional operation, and, besides, does not produce the desired result (in this way the density of the powder explosive material can be increased not more than to 1.3 kg/cm.sup.3, the degree of density being not uniform over the whole length of the charge).
It should be also noted that apart from the above disadvantages of the extended shaped charge in question, the body of the charge, which is assembled from separate components, does not permit the productivity of its manufacture to be considerably raised.